Credit card numbers from some people buying food at University of Southern California dining facilities have been stolen, according to the university.

The theft occurred over a one-month period, said Dan Stimmler, associate senior vice president of auxiliary services. The credit card numbers were obtained due to a breach in third-party software that the university installed three years ago. However, no personal information was compromised, said Stimmler.

He said an investigation has found that the thefts began on May 21–or possibly earlier–and ended June 21 after USC Auxiliary Services discovered the breach and shut down the system.

Faculty, staff, students and visitors were advised to check their credit card statements over the past few months and report any irregularities to their credit card company.

Stimmler said he doesn’t know how many individuals were affected by the thefts, but since the breach occurred after commencement, a time when many students and faculty are off campus, he expects the number to be small.